For producing these decoys, it is known to use emissive blocks contained in an enclosure closed by a nozzle or an orifice forming a nozzle as described in the Patent FR 2,294,422. These blocks are manufactured with a pyrotechnic substance, the combustion of which produces the infra-red radiation.
The decoy is in a launch tube the mouth of which is turned rearwards on the aircraft. The decoy is arranged there in such a way that its rear is on the same side as the mouth of the launch tube. The decoy will be ejected directly into the wind, its direction of movement when it is propelled is close to that of the platform to be protected, at least during the first instance of operation. The front and rear parts of the decoy are identified with respect to its direction of movement over its trajectory in the propelled phase.
After exit from the launch tube, the decoy is stabilised over its trajectory: that is to say that it has no tendency thereon to be affected by a disordered and/or turbulent movement. The Patent EP 0,309,097 describes the stabilisation of the decoy by a telescopic balance weight at the front of the decoy.
The emissive block of the decoy is then fired. The combustion products (gases and particles) accelerated by the nozzle provide the propulsion of the decoy on the one hand and the directive radiation on the other hand. Finally, the nozzle, while providing the directive effect, also diminishes the sensitivity of the flame to the external wind.
A first problem is that the nozzle of this decoy exhibits drawbacks, which are:
presence of an additional mechanical part, which is more or less complicated and thus costly,
presence of an inert mass which makes the decoy heavier,
device whose thrust is not optimal at all altitudes.
A second problem is to ensure the correct ignition of the emissive block.
In fact, according to current practice, (see, for example, Patent FR 2,294,422) the decoy is ignited by the use of the ejection assembly. This assembly is actuated by an ejection charge and it serves as a piston for ejecting the decoy. This ejection assembly includes at least one pyrotechnic delay initiated by the ejection charge. This pyrotechnic delay will ignite the ignition charge arranged in the decoy, the latter charge ensuring the firing of the emissive block.
When the decoy is engaged in the launch tube, its front part turned towards the bottom of the said tube, the previously described arrangement for ensuring the ejection of the decoy and the ignition of the emissive block cannot be used without adding a device which caters for the closing and the sealing of the passage for the ignition gases at the front of the decoy when the latter has to operate.
The separation of the two functions, one of ejection of the decoy, the other of ignition of the emissive block, will pose two other problems, i.e. the increase in the weight of the decoy when a whole ignition assembly, independent of the ejection device, is placed at the front of the decoy as it will not be separable from the decoy, or a less satisfactory ignition of the emissive block when the whole ignition assembly is installed at the rear of the decoy in order to be separated therefrom after ignition of the emissive block.